This paper presents a method to perform a more efficient electromagnetic wave analysis inside a large building by external electromagnetic waves. Topological analysis and the PWB method are introduced for electromagnetic wave analysis. In addition, a Performance- Enhanced PWB method, which complements the performance of the PWB method is proposed. A large virtual structure was selected and an analysis environment was set up to perform the electromagnetic wave analysis inside a large building from external electromagnetic waves. A commercially available software, Wireless Insite, was used to verify the accuracy of the the Performance- Enhanced PWB method. As a result of comparing the two results in terms of accuracy, time, and memory, We conclude that the Performance- Enhanced PWB method proposed in this paper is a more efficient method in a large bulding.